koty: Metalloid

Evidence: 100 • authority: 72

The word metalloid comes from the Latin metallum ("metal") and the Greek oeidḗs ("resembling in form or appearance"). However, there is no standard definition of a metalloid and no complete agreement on which elements are metalloids. Despite the lack of specificity, the term remains in use in the literature. The six commonly recognised metalloids are boron, silicon, germanium, arsenic, antimony and tellurium. Five elements are less frequently so classified: carbon, aluminium, selenium, polonium and astatine. On a standard periodic table, all eleven elements are in a diagonal region of the p-block extending from boron at the upper left to astatine at lower right. Some periodic tables include…

Evidence: 77 • authority: 72

The chemical elements can be broadly divided into metals, metalloids, and nonmetals according to their shared physical and chemical properties. All elemental metals have a shiny appearance (at least when freshly polished); are good conductors of heat and electricity; form alloys with other metallic elements; and have at least one basic oxide. Metalloids are metallic-looking, often brittle solids that are either semiconductors or semimetals, and have amphoteric or weakly acidic oxides. Typical elemental nonmetals have a dull, coloured or colourless appearance; are often brittle when solid; are poor conductors of heat and electricity; and have acidic oxides. Most or some elements in each cate…

Evidence: 60 • authority: 90

Metals and composites in context. Metals and composites in context Junjie Chen Department of Energy and Power Engineering, School of Mechanical and Power Engineering, Henan Polytechnic University, 2000 Century Avenue, Jiaozuo, Henan, 454000, P.R. China Contributor: Junjie Chen, ORCID: 0000-0002-5022-6863, E-mail address: koncjj@gmail.com A metal is a material that, when freshly prepared, polished, or fractured, shows a lustrous appearance, and conducts electricity and heat relatively well. Metals are typically ductile (can be drawn into wires) and malleable (they can be hammered into thin sheets). These properties are the result of the metallic bond between the atoms or molecules of the met…

Evidence: 60 • authority: 72

In the context of the periodic table, a nonmetal is a chemical element that mostly lacks distinctive metallic properties. Physically, nonmetals range from colorless gases such as hydrogen to lustrous crystalline solids such as iodine. They are usually less dense than metals and are often poor conductors of heat and electricity. Chemically, they have moderate to very high electronegativity—a tendency to attract electrons in a chemical bond—and their oxides tend to be acidic. Seventeen elements are widely recognized as nonmetals. Additionally, some or all of six borderline elements (metalloids) are sometimes counted as nonmetals. The two lightest nonmetals, hydrogen and helium, together make…

Evidence: 52 • authority: 72

Zinc is a chemical element; it has the symbol Zn and atomic number 30. It is a slightly brittle metal at room temperature and has a shiny blue whitish appearance when surface oxidation is removed. It is the first element in group 12 (IIB) of the periodic table. Zinc is the 24th most abundant element in Earth's crust, with an average concentration of 70 grams per ton. Zinc also has five stable isotopes; the most abundant of which, zinc-64, comprises nearly half of zinc's total abundance. In some respects, zinc is chemically similar to magnesium: both elements exhibit only one normal oxidation state (+2), and the Zn2+ and Mg2+ ions are of similar size. The most common zinc ore is sphalerite (…

Evidence: 43 • authority: 88

Reduction in the Electromagnetic Interference Generated by AC Overhead Power Lines on Buried Metallic Pipelines with Screening Conductors. This paper presents a numerical study on the reduction in the voltage and current induced on a 13.5 km buried metallic pipeline by an overhead power line. The mitigation effectiveness of different configurations and cross-section shapes of screening conductors is computed by means of a methodology that combines a 2D Finite Element Analysis with circuital analysis. A 35.72% reduction of the maximum induced voltage is obtained when 4 cylindrical steel screening conductors with 8 mm radius are buried 0.25m below the soil surface, along the pipeline path. Th…

Evidence: 43 • authority: 80

Apparatus for Demonstrating that Electricity Develops Only on the Surface of Conductors